The present invention relates to baler twine tensioners, and more specifically relates to a tensioner having the ability to operate satisfactorily when a knot securing ends of the supply rolls of twine passes through the tensioner.
Balers using twine for wrapping the bales produced by them are normally provided with several supply rolls of twine, with a twine end of one roll being secured to a twine end of another roll by tying the ends together with a knot. The twine routing path normally includes one or more tensioners which aid in the control of the twine as it is pulled from the supply rolls. When the knot travels through current twine tensioners, the knot creates a restriction in the tensioner creating a very high twine tension. Typical twine tensioners do not allow the knot to pass through the system without a tremendous increase in the tension and this can result in possible damage, increased wear and/or twine breakage.
The tension of the twine passing through tensioners constructed according to the known designs, (see the tensioner disclosed in U.S. Pat. No. 5,988,053, for example), is directly proportional to the force of a spring or springs used to bias a pair of ribbed rollers together for engaging the twine running between the rollers. Thus, the force acting on the twine is directly related to the roller center distance. In other words, any increase in the roller center distance caused by the twine or a knot creates a direct proportional increase in the twine tension.
Furthermore, due to this increasing force, it is difficult to manually force the ribbed rollers apart in order to thread or route the twine through the tensioner. This procedure is performed by taking a screw driver, pliers or other tool to pry or forcibly spread the rollers apart.
SUMMARY OF THE INVENTION
According to the present invention there is provided an improved baler twine tensioner comprising ribbed rollers biased towards each other.
An object of the invention is to provide a twine tensioner including a pair of ribbed tensioning rolls which are biased together and mounted so as to be able to have a knot pass between them without dramatically increasing twine tension.
A more specific object of the invention is to provide a twine tensioner wherein the movement of one of the ribbed rollers relative to the other is guided by a guide surface which results in a constant run tension over a range of twine sizes, and which operates to permit the center distance of the rollers to increase without resulting in a directly proportional increase of the twine tension. This is accomplished by arranging the guide surface and spring in such relationship to each other that the guide surface causes the spring force to remain substantially constant over the majority of the range of movement normally experienced by the moveable roller. It is conceivable that one or both of the rollers could be mounted to eccentric shafts mounted within a guide surface for pivoting against a resilient force offered by an associated torsion spring, the eccentric shape of the shaft or shafts resulting in the roller or rollers being guided so as to maintain a substantially constant tension force in a length of twine passing through the nip of the rollers, even during the time that the rollers separate to permit a knot in the twine to pass between them.
Yet another object of the invention is to provide a tensioner having a design permitting the moveable ribbed roller to be manually separated from the fixed roller with low force and no tools so as to permit threading of the twine through the tensioner. This is accomplished by mounting a handle to inner roller control or slot plates having the moveable roller mounted between them with its axle projecting through guide slots in respective outer fixed mounting plates, the handle being used to overcome the force of the biasing spring and cause the axle of the moveable roller to move along the guide slots so as to cause a relatively large separation of the tensioner rollers for easy threading of twine between them.
These and other objects of the invention will become apparent from a reading of the ensuing description together with the appended drawings.